The prevention of axillary malodor is a constant objective of scientific endeavor. It has been recognized for some time that sweat itself, as it is excreted from apocrine sweat gland abundantly present in the underarm skin, is generally odorless. Axillary malodor essentially develops upon the metabolic activity of certain strains of bacteria that have evolved to live in this niche environment and which are well adapted to growing on the peculiar cocktail of odorless precursors found in apocrine sweat.
Several classes of malodorous substances have been isolated so far, one class is from steroidic origin, another class encompasses bacterial degradation compounds: short chain fatty acids like (E/Z)-3-methyl-2-hexenoic acid, described as predominant olfactory contributor of the sweat malodor.
A third class of sulfur compounds has only very recently been discovered and has been disclosed independently in WO 200403766, in Troccaz et al., “3-Methyl-3-sulfanylhexan-1-ol as a Major Descriptor for the Human Axilla-Sweat Odor Profile” Chemistry & Biodiversity, Vol. 1 (2004); and in Natsch et al., “Identification of Odoriferous Sulfanylalkanols in Human Axilla Secretions and Their Formation through Cleavage of Cysteine Precursors by a C—S Lyase Isolated from Axilla Bacteria”, Chemistry & Biodiversity, Vol. 1 (2004).
One particularly malodorous specimen of the class of sulfur compounds was found to be 3-methyl-3-sulfanylhexan-1-ol (Troccaz et al., followed by Natsch et al. and Hasegawa et al. “Identification of New Odoriferous Compounds in Human Axillary Sweat” Chemistry and Biodiversity Vol. 1 (2004) 2042-50). The same compound is also disclosed in U.S. Pat. No. 6,610,346, where it is used as a flavor in foods and beverages for providing cooked vegetable (onion) and meaty notes to food products.
Presently, malodor development has been tackled in different ways, for example by applying anti-bacterial substances to the axillary skin, by providing perfume compositions capable of masking malodor, by trapping malodorous molecules, for example by applying cyclodextrin, for inhibiting β-lyases, for example.
With the objective to prevent the formation of volatile sulfur compounds (VSCs) as, for example, S-3-methyl-3-sulfanylhexan-1-ol it becomes indispensable to elucidate its metabolic pathway, and, in particular, its direct precursor. Such insight would allow designing screening for compounds having the ability of intervening in the pathway and thus inhibit the formation of the VSC.
Accordingly, Natsch et al. have speculated that the cysteine conjugate of VSCs (Cys-S-3-methyl-3-sulfanylhexan-1-ol), was the direct precursor for VSCs and that, cleavage of the precursor by a C—S β-lyase present in Corynebacterium spp. would directly yield the VSC.
Similarly, Lyon et al. (U.S. Pat. No. 5,213,791), disclosing amino acid β-lyase inhibitors as deodorants, considered that the Cys-S-conjugate was the most relevant precursor on col. 2, line 5-6. These findings corresponds to the well-reported pathway of thiols and thiolmethyl metabolites starting with glutathione conjugates, which undergoes sequential enzymatic hydrolysis to yield the thioether of cysteine.
A further objective of the present invention is to identify the bacterial species or strains, which are able to convert non-odoriferous precursors of human sweat into malodorous VSCs, allowing to more precisely targeting the origin of malodor development.
Accordingly, Natsch et al. concluded that non-odoriferous precursors of axillary secretions are transformed into volatile substances by bacterial enzymes present only in Corynebacterium spp. and not in staphylococci.
In view of the prior art, the objective of the present invention is to find other, direct precursors of volatile sulfur compounds responsible for axillary malodor. It is a further objective to identify further bacterial strains responsible of producing volatile sulfur compounds. The knowledge on precursors and bacterial strains at the origin of malodorous compounds may then be used to more effectively combat axillary malodor development in humans, for example by providing effective screening methods for compounds inhibiting the formation of VSCs. Therefore, it is a further objective of the present invention to provide new methods or ways for preventing development of malodor.